ZnO metal-semiconductor-metal ultraviolet photodiodes with Au contacts

ZnO epitaxial films were grown on (0001) sapphire substrates by radio-frequency plasma-assisted molecular beam epitaxy. AuZnOAu metal-semiconductor-metal ultraviolet photodiodes with various finger widths and pitches ranging from 10 to 30 μm were also fabricated. It was found that we achieved largest detector responsivity from the 10×10 photodiodes with 10 μm finger width and 10 μm pitch. It was also found that the responsivity increases with the applied bias. With an incident wavelength of 370 nm and 1 V applied bias, it was found that the responsivity for the 10×10 photodiode was 0.135 AW, which corresponds to a quantum efficiency of 44.9%. Furthermore, it was found that noise equivalent power and corresponding detectivity D* of the 10×10 photodiodes were 3.17× 10-13 W and 2.23× 1012 cm Hz0.5 W-1, respectively.